<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div class="container">
        <!-- FFC弹性格式化上下文 -->
        <div class="left">左侧</div>
        <div class="right">右侧</div>
    </div>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        .container{
            display: flex;
            height: 300px;
            width: 600px;
        }
        .left{
            background-color: red;
            flex: 1 2 300px;
        }
       .right{
            background-color: green;
            flex: 2 1 200px;
        }
       
    </style>
</body>
</html>